Abstract: Sealing means for use in the upstream passage of a slide plate screen changer, comprising a ring-shaped seal for contact with the slide plate, a pliable ring and a sleeve. A cavity external to the passage is formed by the seal, the sleeve and a shoulder on the body defining the passage. The pliable ring substantially fills and is confined by the cavity. The sleeve forms an aperture communicating between the passage and the cavity to transmit the pressure in the passage to the pliable ring.

Abstract: Apparatus the temperature of a thermoplastic sheet including a hollow wave guide having a bend therein, for receiving and transmitting infrared energy emitted by the sheet between a sheet heater at a sheet forming station and differential pressure forming apparatus at a forming station. One end of the hollow channel is mounted adjacent the sheet. At the opposite end of the hollow channel, a plurality of infrared energy sensors is mounted for sensing the infrared energy. Infrared sensors include mechanism for converting the infrared energy to electrical energy to operate a control system which controls the level of electrical power to the heater and thus controls the temperature of the sheet.